1. Field of the Invention
The invention relates to check valves of the flapper type.
2. Description of the Prior Art
There are a number of commercially available flapper type check valves having spring loaded half-discs for limiting flow in a piping system to one direction. Those valves are typically of a "wafer" design to fit between pipe end flanges. Among the prior art flapper valves are those of U.S. Pat. Nos. 3,007,488; 3,026,901; 3,072,141; 3,074,427; 3,452,778 and 3,678,958. Prior art valves of the wafer type are adapted for attachment to flanged pipe ends or flanged piping appurtenances and cannot be directly joined to elements having no flanges. Thus two wafer type elements such as a wafer check valve and a wafer butterfly valve cannot be joined together unless an intermediate flanged item is positioned between them. With the modern extensive use of grooved piping elements, it has become desirable to provide a grooved end valve which can be joined to another grooved pipe element
Conventional check valves often have points of possible leakage. In some valves, stops for the valve discs are separate pieces attached to the valve body by fasteners around which leakage can occur. When the hinge shaft of a valve extends through the exterior wall of the valve body there is a possible leakage area at the shaft ends.
Another problem in the use of conventional check valves with one piece valve bodies is that inspection and replacement of the seal, which is bonded to a seat within the body requires working in a "well" where access is awkward.
These and other disadvantages of known check valves are overcome by the provision of a valve according to the present invention.